Illuminator

1. An illuminator comprising: a concave mirror to reflect incident light in a predetermined direction; an inner reflective mirror provided on an optical axis of the concave mirror and having a reflective surface on at least one surface thereof; a light source installed on at least one surface of the inner reflective mirror to generate and illuminate light; and a retro-reflective mirror provided at a focal point of a light reflected from the concave mirror, or in a vicinity of the focal point, and having an aperture through which some of light illuminated from the light source and reflected by the concave mirror passes and a retro-reflective surface to reflect remaining light not passing through the aperture back toward the concave mirror.

2. The illuminator as claimed in claim 1 , wherein the concave mirror is an elliptical mirror having first and second focal points, the light source is approximately disposed at the first focal point to cause the light illuminated from the light source and reflected from the elliptic mirror to be focused in a vicinity of the second focal point, and the retro-reflective mirror is disposed at the second focal point or in the vicinity of the second focal point.

3. The illuminator as claimed in claim 1 , wherein at least one surface of the inner reflective mirror is a flat mirrored disk arranged parallel to an optical axis of the concave mirror.

4. The illuminator as claimed in claim 1 , wherein the retro-reflective surface is flat and arranged perpendicular to an optical axis of incident light, and the aperture is provided at a central portion of the retro-reflective surface and has one of a slit shape, a polygonal shape, a rectangular shape, and a circular shape.

5. The illuminator as claimed in claim 1 , wherein the light source comprises at least one light emitting diode installed on a first surface of the inner reflective mirror or a second surface opposite to the first surface of the inner reflective mirror.

6. The illuminator as claimed in claim 5 , wherein each light emitting diode comprises a light emitting surface equal to or greater than a size of 0.5×0.5 mm 2 .

7. The illuminator as claimed in claim 5 , wherein each light emitting diode illuminates light of one of a white, a red, a orange, a yellow, a green, a cyan, a blue, a violet, an infrared, and an ultraviolet wavelength.

8. The illuminator as claimed in claim 1 , further comprising: an optical integrator provided on a proceeding path of the light passing through the retro-reflective mirror to emit light by mixing incident light.

9. The illuminator as claimed in claim 8 , wherein the optical integrator comprises an incident end portion disposed at a position of the retro-reflective mirror to allow light passing through the aperture to be incident on the optical integrator.

10. The illuminator as claimed in claim 8 , wherein the optical integrator comprises a rod having a rectangular shape, formed of glass or plastic, and to totally reflect incident light therein due to a difference between a refractive index of the rod and a refractive index of a surrounding area of the rod.

11. The illuminator as claimed in claim 8 , wherein the optical integrator comprises a barrel having an inner space through which incident light passes and a reflective portion formed on an inner wall of the barrel to reflect the incident light into uniform light as the incident light proceeds through the inner space.

12. The illuminator as claimed in claim 1 , further comprising an optical fiber to transmit light passing through the aperture and having an incident end portion disposed at a position of the retro-reflective mirror corresponding to the aperture.

13. The illuminator as claimed in claim 12 , wherein the optical fiber is formed of glass or plastic and totally reflects light incident on the incident end portion therein.

14. An illuminator comprising: a first concave mirror having first and second focal points and having a partially oval shape to reflect light incident thereon from the first focal point and a vicinity of the first focal point to proceed toward the second focal point and the vicinity of the second focal point; a first inner reflective mirror disposed on an optical axis of the first concave mirror to reflect incident light toward the first concave mirror; a first light source installed substantially at the first focal point on the first inner reflective mirror to generate and emit light; a retro-reflective mirror provided in the vicinity of the second focal point and having an aperture to pass some of light illuminated from the first light source and reflected by the first concave mirror therethrough and a retro-reflective surface to reflect remaining light of the incident light; a second concave mirror arranged to face the first concave mirror, having a partially oval shape, and having a third focal point and a fourth focal point substantially disposed at the same position of the second focal point, to focus light from the retro-reflection surface on the third focal point or a vicinity of the third focal point and to reflect light incident thereon from the third focal point or the vicinity of the third focal point toward the fourth focal point; and a second inner reflective mirror disposed on an optical axis of the second concave mirror to reflect incident light toward the second concave mirror.

15. The illuminator as claimed in claim 14 , further comprising: a second light source installed substantially at the third focal point on the second inner reflective mirror to generate and emit light.

16. The illuminator as claimed in claim 15 , wherein each of the first and second light sources comprises a light emitting diode.

17. The illuminator as claimed in claim 16 , wherein each light emitting diode comprises a light emitting surface equal to or greater than a size of 0.5×0.5 mm 2 .

18. The illuminator as claimed in claim 16 , wherein each light emitting diode illuminates light of one of a white, a red, an orange, a yellow, a green, a cyan, a blue, a violet, an infrared, and an ultraviolet wavelength.

19. The illuminator as claimed in claim 14 , wherein the second concave mirror is installed to be inclined with respect to the first concave mirror such that a segment connecting the first and second focal points and a segment connecting the third and fourth focal points forms a predetermined angle, and a space is formed between the first and second inner reflective mirrors.

20. The illuminator as claimed in claim 19 , further comprising: a second light source substantially installed at the third focal point on the second inner reflective mirror to illuminate light.

21. The illuminator as claimed in claim 20 , further comprising: a heat sink provided between the first and second inner reflective mirrors to dissipate heat generated from the first and second light sources.

22. The illuminator as claimed in claim 14 , wherein each of the first and second inner reflective mirrors comprises a flat mirror having at least one surface arranged parallel to an optical axis of the respective first and second concave mirrors.

23. The illuminator as claimed in claim 14 , wherein the retro-reflective surface is flat and arranged perpendicular to an optical axis of incident light, and the aperture is provided at a central portion of the retro-reflective surface and has one of a slit shape, a polygonal shape, a rectangular shape, and a circular shape.

24. The illuminator as claimed in claim 14 , further comprising an optical integrator provided on a proceeding path of light passing through the aperture of the retro-reflective mirror to emit uniform light by mixing incident light.

25. The illuminator as claimed in claim 24 , wherein the optical integrator comprises an incident end portion disposed at a position of the retro-reflective mirror to allow light passing through the aperture to be incident on the optical integrator.

26. The illuminator as claimed in claim 24 , wherein the optical integrator comprises a rod having a rectangular shape and formed of glass or plastic to totally reflect incident light therein due to a difference in a refractive index of the rod and a refractive index of a surrounding area of the rod.

27. The illuminator as claimed in claim 24 , wherein the optical integrator comprises a barrel encompassing an inner space through which incident light passes and a reflective portion formed on an inner wall of the barrel to reflect incident light into uniform light as the incident light passes through the inner space.

28. The illuminator as claimed in claim 14 , further comprising an optical fiber to transmit the light passing through the aperture and having an incident end portion disposed at a position of the retro-reflective mirror corresponding to the aperture.

29. The illuminator as claimed in claim 28 , wherein the optical fiber is formed of glass or plastic totally reflect light incident on the incident end portion therein.

30. An illuminator, comprising: a concave reflecting unit to reflect light incident thereon toward a vicinity of a target point and having a concave reflecting unit divider to divide the concave reflecting unit into a first concave reflecting unit and a second concave reflecting unit; and a retro-reflecting unit including an aperture disposed at the target point to pass a portion of the light reflected from the concave reflecting unit therethrough and a retro-reflecting surface to reflect a remaining portion of the light reflected from the concave reflecting unit back towards the concave reflecting unit to be incident thereon.

31. The illuminator as claimed in claim 30 , wherein the concave reflecting unit comprises: an elliptical mirror to reflect light incident thereon toward one of a first focal point and a second focal point disposed at the target point; and an inner reflective mirror surface of the concave reflecting unit divider extending from the elliptical mirror through the first focal point to reflect the light reflected by the elliptical mirror toward the first focal point back to the elliptical mirror to be reflected toward the second focal point.

32. The illuminator as claimed in claim 30 , wherein the concave reflecting unit comprises: a first concave mirror surface of the first concave reflecting unit having a first focal point and a second focal point disposed at the target point and to reflect light incident thereon toward one of the first focal point and the second focal point; a second concave mirror surface of the first concave reflecting unit having a third focal point and a fourth focal point disposed at the target point and to reflect light incident thereon toward one of the third focal point and the fourth focal point; a first inner reflective mirror surface of the concave reflecting unit divider extending from the first concave mirror surface through the first focal point to reflect the light reflected by the first concave mirror surface toward the first focal point back to the first concave mirror surface to be reflected toward the second focal point; and a second reflective mirror surface of the concave reflecting unit divider extending from the second concave mirror surface through the third focal point to reflect the light reflected by the second concave mirror surface toward the third focal point back to the concave mirror surface to be reflected to the fourth focal point.

33. The illuminator as claimed in claim 32 , wherein the first and second inner reflective mirror surfaces are adjacent to and contacting one another.

34. An illuminator, comprising: a first reflecting unit to reflect light incident thereon to a target point and a vicinity of the target point; a second reflecting unit to reflect light incident thereon to the target point and the vicinity of the target point; and a retro-reflecting unit having an aperture disposed at the target point to pass a portion of the light emitted from the first and second reflecting units therethrough and a retro-reflective surface surrounding the aperture to reflect a portion of the light reflected by the first reflecting unit and not passing through the aperture toward the second reflecting unit and to reflect a portion of the light reflected by the second reflected unit and not passing through the aperture toward the first reflecting unit.

35. The illuminator as claimed in claim 34 , wherein: the first reflecting unit comprises a first curved reflecting surface having a first focal point and a second focal point disposed at the target point to reflect light incident thereon from one of the first and second focal points and a vicinity thereof toward the other one of the first and second focal points and a vicinity thereof and a first flat reflecting surface extending from the first curved reflecting surface through the first focal point and the vicinity thereof to reflect light incident thereon toward the first curved reflecting surface; and the second reflecting unit comprises a second curved reflecting surface having a third focal and a fourth focal point disposed at the same position as the target point to reflect light incident thereon from one of the third and fourth focal points and a vicinity thereof toward the other one of the third and fourth focal points and a vicinity thereof and a second flat reflecting surface extending from the second curved reflecting surface through the third focal point and the vicinity thereof to reflect light incident thereon toward the second curved reflecting surface.

36. The illuminator as claimed in claim 34 , wherein the first and second reflecting units are arranged to be adjacent to and contacting each other.

37. The illuminator as claimed in claim 1 , wherein the light source comprises at least one light emitting diode installed on a surface that is planar to the reflective surface of the inner reflective mirror.

38. The illuminator as claimed in claim 1 , wherein the inner reflective mirror is of a semicircular shape having a curved inner edge surface with two ends connected by one outer edge surface.

39. The illuminator as claimed in claim 1 , wherein the curved inner edge surface of the inner reflective mirror corresponds to and abuts with the concave mirror along the entire curved inner edge surface.

40. The illuminator as claimed in claim 30 , wherein the concave reflecting unit divider is installed at an optical axis of the concave reflecting unit.

41. The illuminator as claimed in claim 30 , wherein a light source is installed on one side of the reflecting unit divider.

42. The illuminator as claimed in claim 41 , wherein the light source is installed on a side of the concave reflective unit divider to direct light away from one of the first concave reflecting unit or the second concave reflecting unit.

43. The illuminator as claimed in claim 41 , wherein the light source is installed within the first concave reflecting unit and the divider blocks light emitted from the light source from entering the second concave reflecting unit.

44. The illuminator as claimed in claim 41 , wherein one of the first concave reflecting unit or the second concave reflecting unit does not contain a light source to generate light.